System and method for purifying and preparing high-purity vanadium pentoxide powder

ABSTRACT

The present invention provides a system and method for purifying and preparing vanadium pentoxide powder. Industrial grade vanadium pentoxide is converted to vanadium oxytrichloride by low temperature fluidizing chlorination, wherein chlorinating gas is preheated via heat exchange between fluidizing gas and chlorination flue gas, and an appropriate amount of air is added to enable a part of carbon powder to combust so as to achieve a balanced heat supply during the chlorination, thereby increasing the efficiency of chlorination and ensuring good selectivity in low temperature chlorination. The vanadium oxytrichloride is purified by rectification, and then subjected to fluidized gas phase ammonification, thereby obtaining ammonium metavanadate, and further obtaining a high-purity vanadium pentoxide powder product through fluidized calcination. The system and method have advantages of favorable adaptability to a raw material, no discharge of contaminated wastewater, low energy consumption and chlorine consumption in production, stable product quality and so on.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase entry of InternationalApplication No. PCT/CN2016/072524, filed on Jan. 28, 2016, which isbased upon and claims priority to Chinese Patent Application No.CN201510051577.X, filed on Jan. 30, 2015, the entire contents of whichare incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the fields of chemical engineering andmaterials, and more particularly to a system and method for purifyingand preparing high-purity vanadium pentoxide powder.

BACKGROUND OF THE INVENTION

Vanadium pentoxide is one of the important industrial vanadium products,and widely applied in the production of alloy additives such asferrovanadium and vanadium nitride, and in the fields of catalysts,colorants, cemented carbide additives and the like. With the continuousdevelopment of new energy technologies, there is a growing demand onhigh-purity vanadium pentoxide (with a purity of above 3N5) in thebattery industry, including an all-vanadium redox flow battery (VRB)with good large-scale energy storage performance, a vanadate-basedlithium-ion battery used for electric automobiles and the like. However,in general, only vanadium pentoxide with a purity of 2N5 (i.e. theproduct according with the specification in HGT 3485-2003) can beprepared by the existing industrial technology, which is difficult tomeet requirements on vanadium pentoxide for the battery industry.Therefore, how to prepare high-purity vanadium pentoxide with low costand high efficiency is one of the urgent issues need to be solved in thefield of new energy technologies.

At present, a vanadium-leaching solution or a vanadium solution obtainedby dissolving a vanadium-rich material (such as ammoniumpolyorthovanadate, ammonium metavanadate, industrial grade vanadiumpentoxide, etc.) is usually used as a raw material, and purified by themethods such as chemical precipitation purification and/or solventextraction/ion resin exchange etc. to obtain a purified vanadiumsolution; and then subjected to ammonium salt precipitation to obtainthe purified ammonium polyvanadate or ammonium metavanadate precipitate;then, the precipitate is subjected to decomposition by calcination toobtain the high-purity vanadium pentoxide powder, as described inChinese Patent Applications CN1843938A, CN102730757A, CN103145187A,CN103515642A, CN103194603A, CN103787414A, CN102181635A and CN103663557A,European Patent EP0713257B1, etc. In these methods, the processparameter for impurity removal is closely related to the content of theimpurity in the raw material, thus the adaptability to the raw materialis poor. Moreover, the calcium salt and magnesium salt scavengers orextractants, the acid and alkali reagents and ammonium salts forvanadium precipitation used in the purification process are also liableto introduce impurities. In order to improve the quality of the product,it is usually required to use expensive reagents with high purity,thereby leading to the following problems: the cost is too high,large-scale production cannot be implemented and the purity of theproduct is difficult to stabilize at above 3N5.

For the problems that the scavengers or extractants are liable tointroduce impurities and the cost of the reagents used is too high, therelevant agencies also propose the use of the repeated precipitationmethod to achieve purification and impurity removal of a vanadiumsolution; that is, by using the ammonium salt precipitationcharacteristic of the vanadium-containing solution, vanadium isselectively precipitated out, to confine a part of the impurity ions tothe solution after precipitation; the resulting ammonium saltprecipitate is dissolved and then multiple repeated operations areconducted, to obtain more pure ammonium polyorthovanadate or ammoniummetavanadate precipitate; and the precipitate is subjected todecomposition by calcination to obtain a high-purity vanadium pentoxidepowder, as described in Chinese Patent Applications CN103606694A,CN102923775A, etc. This process effectively reduces the amount of thereagents used and the possibility that the reagents introduceimpurities. However, the dissolution-precipitation process stillrequires use of a large quantity of high-purity acid and alkali reagentsand ammonium salts, therefore the cost of purification is still high;and the cumbersome multiple precipitation operations not only lower theproduction efficiency but also lead to a significant decline in thedirect recovery rate of vanadium. In addition, in the above-mentionedsolution purification methods, extraction/back extraction,precipitation, washing and other operation steps will produce a largeamount of waste water mainly containing a small quantity of vanadiumions and ammonium ions and a large amount of sodium salts, which resultsin difficult treatment and outstanding problem of pollution and alsoseriously restricts the large-scale industrial application of themethods.

Due to the large difference in the boiling points and saturated vaporpressures of metal chlorides, different metal chlorides are easilyseparated by distillation/rectification. Raw materialchlorination—purification by rectification—subsequent treatment is acommonly-used preparation process for high-purity materials such ashigh-purity silicon (polysilicon), high-purity silicon dioxide, and thelike. Because of a very large difference between boiling points of thechloride of vanadium, vanadium oxytrichloride, and the chlorides ofcommon impurities such as iron, calcium, magnesium, aluminum, sodium,potassium and the like, high-purity vanadium oxytrichloride is easilyobtained by rectification, and high-purity vanadium pentoxide can beprepared by subjecting the high-purity vanadium oxytrichloride tohydrolysis and ammonium salt precipitation, supplemented by calcination.Therefore, the use of the chlorination method for the preparation ofhigh-purity vanadium pentoxide has a greater advantage in principle. Infact, the use of the chlorination method for the preparation ofhigh-purity vanadium pentoxide is not only feasible in principle, butalso has been implemented in the laboratory by the researchers of IowaState University in the United States as early as the 1960s (Journal ofthe Less-Common Metals, 1960, 2: 29-35). They employed ammoniumpolyorthovanadate as a raw material, and prepared the crude vanadiumoxytrichloride by chlorination with addition of carbon, then obtainedhigh-purity vanadium oxytrichloride through purification bydistillation, and conducted ammonium salt precipitation to obtainhigh-purity ammonium metavanadate, and finally calcined high-purityammonium metavanadate at 500-600° C., to obtain the high-purity vanadiumpentoxide powder. However, a large amount of wastewater containingammonia and nitrogen will be produced in the precipitation and thewashing processes, leading to difficult treatment. Moreover, the studyonly realizes the intermittent preparation of high-purity vanadiumpentoxide by the chlorination method with the laboratory equipment, andcannot provide related information on how to use the chlorination methodfor continuous preparation of high-purity vanadium pentoxide on anindustrial scale. It may be for exactly these reasons that the report oncontinuous preparation of high-purity vanadium pentoxide by thechlorination method is difficult to find in the decades after the study.

Recently, Chinese Patent Application CN103130279A proposes a method forpreparing high-purity vanadium pentoxide by using the chlorinationmethod with a vanadium-iron magnetic iron ore, vanadium slag,vanadium-containing catalyst and other materials containing vanadium asraw materials. A mixture of chlorides of vanadium is obtained throughchlorination with addition of carbon—dust removal—condensing, andvanadium tetrachloride is separated through rectification to obtain purevanadium oxytrichloride, then the vanadium oxytrichloride is fed into anultrapure aqueous solution or ultrapure aqueous solution of ammonia andprecipitated, and the precipitate is filtered, dried and calcined toobtain vanadium pentoxide. This patent has the following deficiencies:(1) similar to the above study of Iowa State University in the UnitedStates, this patent actually provides the basic flow of chlorinationonly, lacking the specific operable solutions. For example, the methodof chlorination comprises both boiling chlorination and molten saltchlorination, which are completely different methods of chlorination.For another example, concerning the chlorination reactor, it is proposedto use reactors such as “rotary kiln, fluidized furnace, boilingfurnace, shaft furnace, multi-hearth furnace” and the like, whichactually covers almost all of the commonly-used mainstream reactors inthe metallurgical industry; however, different reactors' requirementsfor raw materials differ greatly. For example, the shaft furnace canonly handle “coarse” particles with a particle size more than 8 mm, andneeds to conduct pelleting and sintering pretreatment when “fine”particles are processed, while boiling chlorination is generallysuitable for the treatment of fine particles. Therefore, a particularvanadium raw material cannot be directly applied to rotary kiln,fluidized furnace, boiling furnace, shaft furnace, multi-hearth furnaceand other reactors. Moreover, the “fluidized furnace” and “boilingfurnace” are essentially the same, just different in names; therefore,since these reactors vary widely in operation mode and condition, themethod cannot actually be implemented on the condition that only basicflow is provided. (2) Vanadium oxytrichloride is fed into the ultrapureaqueous solution for hydrolysis. However, because vanadium pentoxide iseasily dissolved in the hydrochloric acid solution, the recovery rate ofprecipitation of vanadium is too low. Moreover, in the hydrochloric acidsolution with an HCl concentration more than 6.0 mol/L, when vanadiumpentoxide is dissolved, it will be reduced to VOCl₂ and chlorine gas isreleased, which will further reduce the recovery rate of precipitationof vanadium. Precipitation and washing processes will inevitably producea large amount of hydrochloric acid solution containing vanadium, and itis difficult to effectively achieve a comprehensive treatment.

In addition, for large-scale industrial applications, there still existsthe following two problems in the existing technologies for chlorinationof vanadium raw materials: (1) calcination for chlorination of vanadiumraw materials is a strong exothermic process, and in addition topreheating the solid and gas reaction materials, the heat generated bythe chlorination reaction still needs to be removed by furnace wall heatdissipation to stabilize the temperature in the chlorination; therefore,both the solid and gas are usually enters the reactor at a temperatureof near room temperature, and only can participate in the reaction afterbeen preheated by the heat produced from the chlorination reaction,resulting in too low efficiency of reaction in part of the chlorinationreactor; (2) since the heat produced by the chlorination reaction needsto be removed through dissipation of a large amount of heat to maintainthe operation temperature, the operating condition and environmentalclimate change are both liable to cause fluctuations in chlorinationtemperature, resulting in reduction of selectivity in chlorination andefficiency, and it is needed to use a reasonable method for balancedsupply of heat and temperature regulation. Therefore, reasonable heatsupply and temperature control must be provided. Only in this way, it ispossible to effectively improve the efficiency of chlorination andobtain stable chlorination temperature, so as to ensure the selectivityin the chlorination to effectively inhibit the chlorination ofimpurities.

Therefore, achieving the regulation of chlorination process, improvingthe direct recovery rate of vanadium, avoiding the production of a largeamount of ammonia-nitrogen wastewater and increasing the efficiency ofpurification of vanadium pentoxide by innovation of the process andtechnology, are the keys to increase the economy of the technology forpurifying and preparing high-purity vanadium pentoxide through thechlorination method.

SUMMARY OF THE INVENTION

In view of the above problem, the present invention proposes a systemand method for purifying and preparing high-purity vanadium pentoxidepowder, to ensure good selectivity in low temperature chlorination,avoid the production of a large amount of wastewater containing ammoniaand nitrogen, and reduce the energy consumption in the production ofhigh-purity vanadium pentoxide and the operation cost. In order toachieve these objects, the present invention adopts the followingtechnical solutions.

The present invention provides a system for purifying and preparinghigh-purity vanadium pentoxide powder, comprising feeding device 1, lowtemperature chlorination fluidized bed 2, rectification and purificationdevice 3, gas phase ammonification fluidized bed 4, ammoniummetavanadate feeding device 5, calcination fluidized bed 6, tail gaswashing absorber 7, induced draft fan and chimney 9;

wherein feeding device 1 comprises industrial grade vanadium pentoxidehopper 1-1, industrial grade vanadium pentoxide screw feeder 1-2, carbonpowder hopper 1-3 and carbon powder screw feeder 1-4;

low temperature chlorination fluidized bed 2 comprises chlorination bedfeeder 2-1, chlorination fluidized bed body 2-2, chlorination bedcyclone separator 2-3, flue gas heat exchanger 2-4, flue gas condenser2-5, chlorination bed acid-seal tank 2-6 and chlorination bed spiralslag-discharging device 2-7;

rectification and purification device 3 comprises distilling still 3-1,rectifying column 3-2, distillate condenser 3-3, reflux liquidcollecting tank 3-4, silicon-containing vanadium oxytrichloride storagetank 3-5, rectification section acid-seal tank 3-6, high-purity vanadiumoxytrichloride condenser 3-7, and high-purity vanadium oxytrichloridestorage tank 3-8;

gas phase ammonification fluidized bed 4 comprises ammonification bedair purifier 4-1, ammonification bed gas heater 4-2, vanadiumoxytrichloride nozzle 4-3, gas phase ammonification fluidized bed body4-4, ammonification bed cyclone separator 4-5, and ammonification beddischarger 4-6;

ammonium metavanadate feeding device 5 comprises ammonium metavanadatehopper 5-1 and ammonium metavanadate screw feeder 5-2;

calcination fluidized bed 6 comprises calcination bed air purifier 6-1,calcination bed gas heater 6-2, calcination bed feeder 6-3, calcinationfluidized bed body 6-4, calcination bed cyclone separator 6-5 andhigh-purity vanadium pentoxide hopper 6-6;

wherein a feed outlet at the bottom of industrial grade vanadiumpentoxide hopper 1-1 is connected with a feed inlet of industrial gradevanadium pentoxide screw feeder 1-2; a feed outlet at the bottom ofcarbon powder hopper 1-3 is connected with a feed inlet of carbon powderscrew feeder 1-4; and a feed outlet of industrial grade vanadiumpentoxide screw feeder 1-2 and a feed outlet of carbon powder screwfeeder 1-4 are both connected with a feed inlet of chlorination bedfeeder 2-1 through a pipeline;

a feed discharge opening of chlorination bed feeder 2-1 is connectedwith a feed inlet at the upper part of chlorination fluidized bed body2-2 through a pipeline; a gas inlet at the bottom of chlorination bedfeeder 2-1 is connected with a nitrogen gas source main pipe through apipeline; chlorination bed cyclone separator 2-3 is provided at thecenter of the top of the expansion section of chlorination fluidized bedbody 2-2; a gas outlet at the top of chlorination bed cyclone separator2-3 is connected with a hot flue gas inlet of flue gas heat exchanger2-4 through a pipeline; a cold flue gas outlet of flue gas heatexchanger 2-4 is connected with a gas inlet of flue gas condenser 2-5through a pipeline; a gas outlet of flue gas condenser 2-5 is connectedwith a gas inlet of chlorination bed acid-seal tank 2-6 through apipeline; a gas outlet of chlorination bed acid-seal tank 2-6 isconnected with a gas inlet of tail gas washing absorber 7 through apipeline; a slag-discharge opening at the lower part of chlorinationfluidized bed body 2-2 is connected with a feed inlet of chlorinationbed spiral slag-discharging device 2-7 through a pipeline; a gas inletat the bottom of chlorination fluidized bed body 2-2 is connected with ahot gas outlet of flue gas heat exchanger 2-4 through a pipeline; and acold gas inlet of flue gas heat exchanger 2-4 is connected with achlorine gas source main pipe, the nitrogen gas source main pipe and acompressed air main pipe through pipelines, respectively;

a liquid outlet at the bottom of flue gas condenser 2-5 is connectedwith a feed inlet of rectifying column 3-2 through a pipeline; a steamoutlet of distilling still 3-1 is connected with a steam inlet ofrectifying column 3-2 through a pipeline; a backflow inlet of distillingstill 3-1 is connected with a liquid reflux outlet at the bottom ofrectifying column 3-2 through a pipeline; a gas outlet at the top ofrectifying column 3-2 is connected with a gas inlet of distillatecondenser 3-3 through a pipeline; a liquid outlet of distillatecondenser 3-3 is connected with a liquid inlet of reflux liquidcollecting tank 3-4 through a pipeline; a reflux liquid outlet of refluxliquid collecting tank 3-4 is connected with a reflux liquid inlet atthe top of rectifying column 3-2 through a pipeline; a feed dischargeopening of reflux liquid collecting tank 3-4 is connected with an inletof silicon-containing vanadium oxytrichloride storage tank 3-5 through apipeline; an exhaust gas outlet of silicon-containing vanadiumoxytrichloride storage tank 3-5 is connected with a gas inlet ofrectification section acid-seal tank 3-6 through a pipeline; a gasoutlet of rectification section acid-seal tank 3-6 is connected with agas inlet of tail gas washing absorber 7 through a pipeline; arectificate outlet of rectifying column 3-2 is connected with a gasinlet of high-purity vanadium oxytrichloride condenser 3-7 through apipeline; a liquid outlet of high-purity vanadium oxytrichloridecondenser 3-7 is connected with a liquid inlet of high-purity vanadiumoxytrichloride storage tank 3-8 through a pipeline; and an underflowoutlet is provided at the bottom of distilling still 3-1;

a gas inlet of ammonification bed air purifier 4-1 is connected with thecompressed air main pipe through a pipeline; a gas outlet ofammonification bed air purifier 4-1 is connected with a gas inlet ofammonification bed gas heater 4-2, a gas inlet of vanadiumoxytrichloride nozzle 4-3, and a gas inlet at the bottom ofammonification bed discharger 4-6 through pipelines, respectively; thegas inlet of ammonification bed gas heater 4-2 is connected with anultrapure water main pipe and a purified liquid ammonia main pipethrough pipelines; a combustion-supporting wind inlet and a fuel inletof a combustion nozzle of ammonification bed gas heater 4-2 arerespectively connected with the compressed air main pipe and a fuel mainpipe through pipelines; a gas outlet of ammonification bed gas heater4-2 is connected with a gas inlet at the bottom of gas phaseammonification fluidized bed body 4-4 through a pipeline; a liquidoutlet of high-purity vanadium oxytrichloride storage tank 3-8 isconnected with a vanadium oxytrichloride inlet of vanadiumoxytrichloride nozzle 4-3 through a pipeline; ammonification bed cycloneseparator 4-5 is provided at the center of the top of the expansionsection of gas phase ammonification fluidized bed body 4-4; a gas outletat the top of ammonification bed cyclone separator 4-5 is connected witha tail gas treatment unit through a pipeline; a feed discharge openingat the upper part of gas phase ammonification fluidized bed body 4-4 isconnected with a feed inlet of ammonification bed discharger 4-6 througha pipeline; and a feed discharge opening of ammonification beddischarger 4-6 is connected with a feed inlet of ammonium metavanadatehopper 5-1 through a pipeline;

a feed outlet at the bottom of ammonium metavanadate hopper 5-1 isconnected with a feed inlet of ammonium metavanadate screw feeder 5-2;and a feed discharge opening of ammonium metavanadate screw feeder 5-2is connected with a feed inlet of calcination bed feeder 6-3 through apipeline;

a gas inlet of calcination bed air purifier 6-1 is connected with thecompressed air main pipe through a pipeline; a gas outlet of calcinationbed air purifier 6-1 is connected with a gas inlet of calcination bedgas heater 6-2 and a gas inlet at the bottom of calcination bed feeder6-3 through pipelines, respectively; a combustion-supporting wind inletand a fuel inlet of a combustion nozzle of calcination bed gas heater6-2 are respectively connected with the compressed air main pipe and thefuel main pipe through pipelines; a gas outlet of calcination bed gasheater 6-2 is connected with a gas inlet at the bottom of calcinationfluidized bed body 6-4 through a pipeline; a feed discharge opening ofcalcination bed feeder 6-3 is connected with a feed inlet at the lowerpart of calcination fluidized bed body 6-4 through a pipeline; a gasoutlet at the top of calcination fluidized bed body 6-4 is connectedwith a gas inlet of calcination bed cyclone separator 6-5 through apipeline; a powder outlet at the bottom of calcination bed cycloneseparator 6-5 is connected with a feed inlet of an ammonium chloridehopper through a pipeline; a gas outlet at the top of calcination bedcyclone separator 6-5 is connected with the tail gas treatment unitthrough a pipeline; and a feed discharge opening at the upper part ofcalcination fluidized bed body 6-4 is connected with a feed inlet ofhigh-purity vanadium pentoxide hopper 6-6 through a pipeline;

a gas outlet of tail gas washing absorber 7 is connected with a gasinlet of induced draft fan 8 through a pipeline; and a gas outlet ofinduced draft fan 8 is connected with a gas inlet at the bottom ofchimney 9 through a pipeline.

The present invention further provides a method for purifying andpreparing high-purity vanadium pentoxide powder based on the abovesystem, comprising the following steps:

allowing industrial grade vanadium pentoxide powder in industrial gradevanadium pentoxide hopper 1-1 and carbon powder in carbon powder hopper1-3 to enter chlorination bed feeder 2-1 simultaneously throughindustrial grade vanadium pentoxide screw feeder 1-2 and carbon powderscrew feeder 1-4 respectively and be mixed therein, and then enterchlorination fluidized bed body 2-2; allowing chlorine gas from thechlorine gas source main pipe, nitrogen gas from the nitrogen gas sourcemain pipe and air from the compressed air main pipe to be preheated byexchanging heat with chlorination flue gas by flue gas heat exchanger2-4, and then enter chlorination fluidized bed body 2-2 to allow thevanadium pentoxide, the carbon powder and other powder materials to bekept at a fluidized state and chemically reacted, wherein the airenables a part of the carbon powder to combust to provide heat formaintaining the temperature of the fluid bed, and the chlorine gas andthe carbon powder function together to make vanadium pentoxide and asmall amount of impurities chlorinated, to form chlorinated residues andchlorination flue gas rich in vanadium oxytrichloride; discharging thechlorinated residues through the slag-discharge opening at the lowerpart of chlorination fluidized bed body 2-2 and chlorination bed spiralslag-discharging device 2-7; and allowing the chlorination flue gas tobe subjected to dust removing by chlorination bed cyclone separator 2-3and fall back to chlorination fluidized bed body 2-2, and then beprecooled by flue gas heat exchanger 2-4 and enter flue gas condenser2-5, such that vanadium oxytrichloride therein is condensed to form acrude vanadium oxytrichloride liquid and the remaining tail gas enterstail gas washing absorber 7 through chlorination bed acid-seal tank 2-6;

allowing the crude vanadium oxytrichloride liquid formed by flue gascondenser 2-5 to enter rectifying column 3-2 and distilling still 3-1 tobe subjected to rectification operation, to obtain a vanadium-rich wasterich in high-boiling-point impurity, silicon-containing vanadiumoxytrichloride vapor rich in low-boiling-point impurities andhigh-purity vanadium oxytrichloride vapor, wherein the vanadium-richwaste is used for the subsequent recovery of vanadium; condensing thesilicon-containing vanadium oxytrichloride vapor into liquid bydistillate condenser 3-3, wherein a part of the liquid returns torectifying column 3-2 through reflux liquid collecting tank 3-4, and theremaining liquid enters silicon-containing vanadium oxytrichloridestorage tank 3-5; transmitting the exhaust gas produced insilicon-containing vanadium oxytrichloride storage tank 3-5 to tail gaswashing absorber 7 through rectification section acid-seal tank 3-6,wherein silicon-containing vanadium oxytrichloride can be applied in thefield of chemical engineering such as the field of catalysis; andcondensing the high-purity vanadium oxytrichloride vapor into liquid byhigh-purity vanadium oxytrichloride condenser 3-7 and allowing theliquid to enter high-purity vanadium oxytrichloride storage tank 3-8;

allowing the high-purity vanadium oxytrichloride from high-purityvanadium oxytrichloride storage tank 3-8 to be carried by purified airfrom ammonification bed air purifier 4-1 into gas phase ammonificationfluidized bed body 4-4 via vanadium oxytrichloride nozzle 4-3;preheating ultrapure water, purified liquid ammonia and the purified airby ammonification bed gas heater 4-2 and then transmitting them to gasphase ammonification fluidized bed body 4-4, to keep the powder in thebed at a fluidized state and subject vanadium oxytrichloride tohydrolysis and ammonification to generate ammonium metavanadate powdercontaining ammonium chloride, wherein the ammonium metavanadate powdercontaining ammonium chloride enters ammonium metavanadate hopper 5-1after discharged by ammonification bed discharger 4-6, and the producedammonia-containing ammonified flue gas is subjected to dust removing byammonification bed cyclone separator 4-5 and then transmitted to thetail gas treatment unit for treatment;

allowing the ammonium metavanadate powder containing ammonium chloridein ammonium metavanadate hopper 5-1 to enter calcination fluidized bedbody 6-4 through ammonium metavanadate screw feeder 5-2 and calcinationbed feeder 6-3 in turn; allowing compressed air to be purified bycalcination bed air purifier 6-1 and preheated by calcination bed gasheater 6-2 in turn and then enter calcination fluidized bed body 6-4, tokeep the powder in the bed at a fluidized state and subject the ammoniummetavanadate material containing ammonium chloride to thermaldecomposition to obtain a high-purity vanadium pentoxide powder product,and allowing the product to enter high-purity vanadium pentoxide hopper6-6 through the feed discharge opening at the upper part of calcinationfluidized bed body 6-4; allowing the calcination flue gas produced bythe calcination decomposition to enter calcination bed cyclone separator6-5 and be cooled down to separate out ammonium chloride, andtransmitting the calcination flue gas to the tail gas treatment unit fortreatment after dust removal; and transmitting the ammonium chloridepowder collected by calcination bed cyclone separator 6-5 to theammonium chloride hopper;

transmitting the gas discharged from tail gas washing absorber 7 afterabsorption treatment with an alkali solution to chimney 9 then to ventthrough induced draft fan 8.

The first characteristic of the present invention lies in that: inchlorination fluidized bed body 2-2, the amount of the carbon powderadded in the chlorination process is 10%-20% of the mass of theindustrial grade vanadium pentoxide powder; and in the chlorination, theoperation temperature is 300-500° C. and the average residence time ofthe powder is 30-80 min.

The second characteristic of the present invention lies in that: inrectifying column 3-2, the number of trays in the rectification sectionis 5-10, and the number of trays in the stripping section is 10-20 inthe rectification operation; and in the rectification operation, thereflux ratio (i.e., the ratio of the quantity of reflux at the top ofthe column to the amount of the discharged material) is kept at 15-40.

The third characteristic of the present invention lies in that: in gasphase ammonification fluidized bed body 4-4, ammonium metavanadate isprepared by gas phase ammonification of the high-purity vanadiumoxytrichloride, and in the gas phase ammonification, the operationtemperature is 130-250° C., the molar ratio of water vapor to ammoniagas is 0.5-0.8, and the molar ratio of ammonia gas to vanadiumoxytrichloride is 3.5-4.5.

The fourth characteristic of the present invention lies in that: incalcination fluidized bed body 6-4, the thermal decomposition of theammonium metavanadate containing ammonium chloride is achieved byfluidization calcination, and in the calcination, the operationtemperature is 400-650° C., and the average residence time of the powderis 60-180 min.

The purity of the high-purity vanadium pentoxide powder prepared by thepresent invention is above 4N. Compared with the prior art, the presentinvention has the following outstanding advantages:

(1) Through heat exchange between the chlorinating gas and thechlorination flue gas, preheating of the chlorinating gas is achievedwhile the flue gas is cooled, which makes the temperature distributionin the chlorination reactor more uniform, thereby improving theefficiency of low temperature chlorination of vanadium raw materialeffectively.

(2) By adding an appropriate amount of air to enable a part of carbonpowder to combust, a balanced heat supply and temperature regulationduring the chlorination are implemented, thereby stabilizing theoperation temperature in the chlorination, increasing the efficiency ofthe chlorination reaction, ensuring good selectivity in thechlorination, and avoiding side reactions such as generation of vanadiumtetrachloride.

(3) By transmitting vanadium oxytrichloride which is purified byrectification to the gas phase ammonification fluidized bed via thenozzle to conduct hydrolysis and ammonification on the vanadiumoxytrichloride, an ammonium metavanadate powder containing ammoniumchloride is obtained. As compared to the traditional hydrolysis/ammoniumsalt precipitation, the production of ammonium chloride waste saltywater can be avoided effectively.

(4) By conducting fluidization calcination on the ammonium metavanadatecontaining ammonium chloride, ammonium metavanadate is decomposed intothe high-purity vanadium pentoxide product, and ammonium chloride isalso decomposed and discharged with the flue gas, and an ammoniumchloride product can be obtained after cooling, thereby realizing thepreparation of a high-purity product and recovery of ammonium chlorideeffectively.

The present invention has the advantages of favorable adaptability to araw material, good selectivity in low temperature chlorination, nodischarge of contaminated wastewater, low energy consumption inproduction and low operation cost, stable product quality and so on, andis suitable for the large scale industrial production of the high-purityvanadium pentoxide powder with a purity of above 4N, with good economicefficiency and social benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing is used to provide further illustration of thepresent invention and constitutes a part of the specification. It isused to explain the present invention together with the examples of thepresent invention, rather than limit the present invention.

FIG. 1 is a schematic diagram illustrating the configuration of a systemfor producing high-purity vanadium tetraoxide powder according to thepresent invention.

REFERENCE SIGNS

-   -   1 Feeding device    -   1-1 Industrial grade vanadium pentoxide hopper    -   1-2 Industrial grade vanadium pentoxide screw feeder    -   1-3 Carbon powder hopper    -   1-4 Carbon powder screw feeder    -   2 Low temperature chlorination fluidized bed    -   2-1 Chlorination bed feeder    -   2-2 Chlorination fluidized bed body    -   2-3 Chlorination bed cyclone separator    -   2-4 Flue gas heat exchanger    -   2-5 Flue gas condenser    -   2-6 Chlorination bed acid-seal tank    -   2-7 Chlorination bed spiral slag-discharging device    -   3 Rectification and purification device    -   3-1 Distilling still    -   3-2 Rectifying column    -   3-3 Distillate condenser    -   3-4 Reflux liquid collecting tank    -   3-5 Silicon-containing vanadium oxytrichloride storage tank    -   3-6 Rectification section acid-seal tank    -   3-7 High-purity vanadium oxytrichloride condenser    -   3-8 High-purity vanadium oxytrichloride storage tank    -   4 Gas phase ammonification fluidized bed    -   4-1 Ammonification bed air purifier    -   4-2 Ammonification bed gas heater    -   4-3 Vanadium oxytrichloride nozzle    -   4-4 Gas phase ammonification fluidized bed body    -   4-5 Ammonification bed cyclone separator    -   4-6 Ammonification bed discharger    -   5 Ammonium metavanadate feeding device    -   5-1 Ammonium metavanadate hopper    -   5-2 Ammonium metavanadate screw feeder    -   6 Calcination fluidized bed    -   6-1 Calcination bed air purifier    -   6-2 Calcination bed gas heater    -   6-3 Calcination bed feeder    -   6-4 Calcination fluidized bed body    -   6-5 Calcination bed cyclone separator    -   6-6 High-purity vanadium pentoxide hopper    -   7 Tail gas washing absorber    -   8 Induced draft fan    -   9 Chimney

DETAILED DESCRIPTION OF THE INVENTION

In order to make the object, technical solution and advantages of thepresent invention be clearer, the technical solution in the examples ofthe present invention will be described clearly and completely belowwith reference to the accompanying drawing of the examples of thepresent invention. Obviously, the described examples are only a part ofthe examples of the present invention, not all examples. It is worthnoting that the examples are merely used for illustrating the technicalsolution of the present invention, rather than limiting the presentinvention. FIG. 1 is a schematic diagram illustrating a system forpurifying and preparing high-purity vanadium pentoxide powder accordingto the present invention.

Referring to FIG. 1, the system for purifying and preparing high-purityvanadium pentoxide powder used in this example comprises feeding device1, low temperature chlorination fluidized bed 2, rectification andpurification device 3, gas phase ammonification fluidized bed 4,ammonium metavanadate feeding device 5, calcination fluidized bed 6,tail gas washing absorber 7, induced draft fan 8 and a chimney 9;

wherein feeding device 1 comprises industrial grade vanadium pentoxidehopper 1-1, industrial grade vanadium pentoxide screw feeder 1-2, carbonpowder hopper 1-3 and carbon powder screw feeder 1-4;

low temperature chlorination fluidized bed 2 comprises chlorination bedfeeder 2-1, chlorination fluidized bed body 2-2, chlorination bedcyclone separator 2-3, flue gas heat exchanger 2-4, flue gas condenser2-5, chlorination bed acid-seal tank 2-6 and chlorination bed spiralslag-discharging device 2-7;

rectification and purification device 3 comprises distilling still 3-1,rectifying column 3-2, distillate condenser 3-3, reflux liquidcollecting tank 3-4, silicon-containing vanadium oxytrichloride storagetank 3-5, rectification section acid-seal tank 3-6, high-purity vanadiumoxytrichloride condenser 3-7, and high-purity vanadium oxytrichloridestorage tank 3-8;

gas phase ammonification fluidized bed 4 comprises ammonification bedair purifier 4-1, ammonification bed gas heater 4-2, vanadiumoxytrichloride nozzle 4-3, gas phase ammonification fluidized bed body4-4, ammonification bed cyclone separator 4-5, and ammonification beddischarger 4-6;

ammonium metavanadate feeding device 5 comprises ammonium metavanadatehopper 5-1 and ammonium metavanadate screw feeder 5-2;

calcination fluidized bed 6 comprises calcination bed air purifier 6-1,calcination bed gas heater 6-2, calcination bed feeder 6-3, calcinationfluidized bed body 6-4, calcination bed cyclone separator 6-5 andhigh-purity vanadium pentoxide hopper 6-6;

wherein a feed outlet at the bottom of industrial grade vanadiumpentoxide hopper 1-1 is connected with a feed inlet of industrial gradevanadium pentoxide screw feeder 1-2; a feed outlet at the bottom ofcarbon powder hopper 1-3 is connected with a feed inlet of carbon powderscrew feeder 1-4; and a feed outlet of industrial grade vanadiumpentoxide screw feeder 1-2 and a feed outlet of carbon powder screwfeeder 1-4 are both connected with a feed inlet of chlorination bedfeeder 2-1 through a pipeline;

a feed discharge opening of chlorination bed feeder 2-1 is connectedwith a feed inlet at the upper part of chlorination fluidized bed body2-2 through a pipeline; a gas inlet at the bottom of chlorination bedfeeder 2-1 is connected with a nitrogen gas source main pipe through apipeline; chlorination bed cyclone separator 2-3 is provided at thecenter of the top of the expansion section of chlorination fluidized bedbody 2-2; a gas outlet at the top of chlorination bed cyclone separator2-3 is connected with a hot flue gas inlet of flue gas heat exchanger2-4 through a pipeline; a cold flue gas outlet of flue gas heatexchanger 2-4 is connected with a gas inlet of flue gas condenser 2-5through a pipeline; a gas outlet of flue gas condenser 2-5 is connectedwith a gas inlet of chlorination bed acid-seal tank 2-6 through apipeline; a gas outlet of chlorination bed acid-seal tank 2-6 isconnected with a gas inlet of tail gas washing absorber 7 through apipeline; a slag-discharge opening at the lower part of chlorinationfluidized bed body 2-2 is connected with a feed inlet of chlorinationbed spiral slag-discharging device 2-7 through a pipeline; a gas inletat the bottom of chlorination fluidized bed body 2-2 is connected with ahot gas outlet of flue gas heat exchanger 2-4 through a pipeline; and acold gas inlet of flue gas heat exchanger 2-4 is connected with achlorine gas source main pipe, the nitrogen gas source main pipe and acompressed air main pipe through a pipeline, respectively;

a liquid outlet at the bottom of flue gas condenser 2-5 is connectedwith a feed inlet of rectifying column 3-2 through a pipeline; a steamoutlet of distilling still 3-1 is connected with a steam inlet ofrectifying column 3-2 through a pipeline; a backflow inlet of distillingstill 3-1 is connected with a liquid reflux outlet at the bottom ofrectifying column 3-2 through a pipeline; a gas outlet at the top ofrectifying column 3-2 is connected with a gas inlet of distillatecondenser 3-3 through a pipeline; a liquid outlet of distillatecondenser 3-3 is connected with a liquid inlet of reflux liquidcollecting tank 3-4 through a pipeline; a reflux liquid outlet of refluxliquid collecting tank 3-4 is connected with a reflux liquid inlet atthe top of rectifying column 3-2 through a pipeline; a feed dischargeopening of reflux liquid collecting tank 3-4 is connected with an inletof silicon-containing vanadium oxytrichloride storage tank 3-5 through apipeline; an exhaust gas outlet of silicon-containing vanadiumoxytrichloride storage tank 3-5 is connected with a gas inlet ofrectification section acid-seal tank 3-6 through a pipeline; a gasoutlet of rectification section acid-seal tank 3-6 is connected with agas inlet of tail gas washing absorber 7 through a pipeline; arectificate outlet of rectifying column 3-2 is connected with a gasinlet of high-purity vanadium oxytrichloride condenser 3-7 through apipeline; a liquid outlet of high-purity vanadium oxytrichloridecondenser 3-7 is connected with a liquid inlet of high-purity vanadiumoxytrichloride storage tank 3-8 through a pipeline; and an underflowoutlet is provided at the bottom of distilling still 3-1;

a gas inlet of ammonification bed air purifier 4-1 is connected with thecompressed air main pipe through a pipeline; a gas outlet ofammonification bed air purifier 4-1 is connected with a gas inlet ofammonification bed gas heater 4-2, a gas inlet of vanadiumoxytrichloride nozzle 4-3, and a gas inlet at the bottom ofammonification bed discharger 4-6 through a pipeline, respectively; thegas inlet of ammonification bed gas heater 4-2 is connected with aultrapure water main pipe and a purified liquid ammonia main pipethrough a pipeline; a combustion-supporting wind inlet and a fuel inletof a combustion nozzle of ammonification bed gas heater 4-2 arerespectively connected with the compressed air main pipe and a fuel mainpipe through a pipeline; a gas outlet of ammonification bed gas heater4-2 is connected with a gas inlet at the bottom of gas phaseammonification fluidized bed body 4-4 through a pipeline; a liquidoutlet of high-purity vanadium oxytrichloride storage tank 3-8 isconnected with a vanadium oxytrichloride inlet of vanadiumoxytrichloride nozzle 4-3 through a pipeline; ammonification bed cycloneseparator 4-5 is provided at the center of the top of the expansionsection of gas phase ammonification fluidized bed body 4-4; a gas outletat the top of ammonification bed cyclone separator 4-5 is connected witha tail gas treatment unit through a pipeline; a feed discharge openingat the upper part of gas phase ammonification fluidized bed body 4-4 isconnected with a feed inlet of ammonification bed discharger 4-6 througha pipeline; and a feed discharge opening of ammonification beddischarger 4-6 is connected with a feed inlet of ammonium metavanadatehopper 5-1 through a pipeline;

a feed outlet at the bottom of ammonium metavanadate hopper 5-1 isconnected with a feed inlet of ammonium metavanadate screw feeder 5-2;and a feed discharge opening of ammonium metavanadate screw feeder 5-2is connected with a feed inlet of calcination bed feeder 6-3 through apipeline;

a gas inlet of calcination bed air purifier 6-1 is connected with thecompressed air main pipe through a pipeline; a gas outlet of calcinationbed air purifier 6-1 is connected with a gas inlet of calcination bedgas heater 6-2 and a gas inlet at the bottom of calcination bed feeder6-3 through a pipeline, respectively; a combustion-supporting wind inletand a fuel inlet of a combustion nozzle of calcination bed gas heater6-2 are respectively connected with the compressed air main pipe and thefuel main pipe through a pipeline; a gas outlet of calcination bed gasheater 6-2 is connected with a gas inlet at the bottom of calcinationfluidized bed body 6-4 through a pipeline; a feed discharge opening ofcalcination bed feeder 6-3 is connected with a feed inlet at the lowerpart of calcination fluidized bed body 6-4 through a pipeline; a gasoutlet at the top of calcination fluidized bed body 6-4 is connectedwith a gas inlet of calcination bed cyclone separator 6-5 through apipeline; a powder outlet at the bottom of calcination bed cycloneseparator 6-5 is connected with a feed inlet of an ammonium chloridehopper through a pipeline; a gas outlet at the top of calcination bedcyclone separator 6-5 is connected with the tail gas treatment unitthrough a pipeline; and a feed discharge opening at the upper part ofcalcination fluidized bed body 6-4 is connected with a feed inlet ofhigh-purity vanadium pentoxide hopper 6-6 through a pipeline;

a gas outlet of tail gas washing absorber 7 is connected with a gasinlet of induced draft fan 8 through a pipeline; and a gas outlet ofinduced draft fan 8 is connected with a gas inlet at the bottom ofchimney 9 through a pipeline.

The above system is used in this example to purify and preparehigh-purity vanadium pentoxide powder. The specific method comprises thefollowing steps. Industrial grade vanadium pentoxide powder inindustrial grade vanadium pentoxide hopper 1-1 and carbon powder incarbon powder hopper 1-3 enter chlorination bed feeder 2-1simultaneously through industrial grade vanadium pentoxide screw feeder1-2 and carbon powder screw feeder 1-4 respectively and are mixedtherein, and then enter chlorination fluidized bed body 2-2; chlorinegas from the chlorine gas source main pipe, nitrogen gas from thenitrogen gas source main pipe and air from the compressed air main pipeare preheated by exchanging heat with chlorination flue gas by flue gasheat exchanger 2-4, and then enter chlorination fluidized bed body 2-2to allow the vanadium pentoxide, the carbon powder and other powdermaterials at a fluidized state and chemically reacted, wherein the airenables a part of the carbon powder to combust to provide heat formaintaining the temperature of the fluid bed, and the chlorine gas andthe carbon powder function together to make vanadium pentoxide and asmall amount of impurities [[be]] chlorinated, to form chlorinatedresidues and chlorination flue gas rich in vanadium oxytrichloride; thechlorinated residues are discharged through the slag-discharge openingat the lower part of chlorination fluidized bed body 2-2 andchlorination bed spiral slag-discharging device 2-7; and thechlorination flue gas is subjected to dust removing by chlorination bedcyclone separator 2-3 and falls back to chlorination fluidized bed body2-2, and then is precooled by flue gas heat exchanger 2-4 and entersflue gas condenser 2-5, such that vanadium oxytrichloride therein iscondensed to form a crude vanadium oxytrichloride liquid and theremaining tail gas enters tail gas washing absorber 7 throughchlorination bed acid-seal tank 2-6;

the crude vanadium oxytrichloride liquid formed by flue gas condenser2-5 enters rectifying column 3-2 and distilling still 3-1 to besubjected to rectification operation, to obtain a vanadium-rich wasterich in high-boiling-point impurities, silicon-containing vanadiumoxytrichloride vapor rich in low-boiling-point impurities andhigh-purity vanadium oxytrichloride vapor, wherein the vanadium-richwaste is used for the subsequent recovery of vanadium; thesilicon-containing vanadium oxytrichloride vapor is condensed intoliquid by distillate condenser 3-3, wherein a part of the liquid returnsto rectifying column 3-2 through reflux liquid collecting tank 3-4, andthe remaining liquid enters silicon-containing vanadium oxytrichloridestorage tank 3-5; the exhaust gas produced in silicon-containingvanadium oxytrichloride storage tank 3-5 is transmitted to tail gaswashing absorber 7 through rectification section acid-seal tank 3-6,wherein the silicon-containing vanadium oxytrichloride can be applied inthe field of chemical engineering such as the field of catalysis; andthe high-purity vanadium oxytrichloride vapor is condensed into liquidby high-purity vanadium oxytrichloride condenser 3-7 and then enters thehigh-purity vanadium oxytrichloride storage tank 3-8;

the high-purity vanadium oxytrichloride from high-purity vanadiumoxytrichloride storage tank 3-8 is carried by purified air fromammonification bed air purifier 4-1 into gas phase ammonificationfluidized bed body 4-4 via vanadium oxytrichloride nozzle 4-3; ultrapurewater, purified liquid ammonia and the purified air are preheated byammonification bed gas heater 4-2 and then transmitted to gas phaseammonification fluidized bed body 4-4, to keep the powder in the bed ata fluidized state and subject vanadium oxytrichloride to hydrolysis andammonification to generate ammonium metavanadate powder containingammonium chloride, wherein the ammonium metavanadate powder containingammonium chloride enters ammonium metavanadate hopper 5-1 afterdischarged by ammonification bed discharger 4-6, and the producedammonia-containing ammonified flue gas is subjected to dust removing byammonification bed cyclone separator 4-5 and then transmitted to thetail gas treatment unit for treatment;

the ammonium metavanadate powder containing ammonium chloride inammonium metavanadate hopper 5-1 enters calcination fluidized bed body6-4 through ammonium metavanadate screw feeder 5-2 and calcination bedfeeder 6-3 in turn; compressed air is purified by calcination bed airpurifier 6-1 and preheated by calcination bed gas heater 6-2 in turn andthen enters calcination fluidized bed body 6-4, to keep the powder inthe bed at a fluidized state and subject the ammonium metavanadatematerial containing ammonium chloride to thermal decomposition to obtaina high-purity vanadium pentoxide powder product, and the product entershigh-purity vanadium pentoxide hopper 6-6 through the feed dischargeopening at the upper part of calcination fluidized bed body 6-4; thecalcination flue gas produced from the calcination decomposition enterscalcination bed cyclone separator 6-5 and be cooled down therein, suchthat ammonium chloride is separated out, and the calcination flue gas istransmitted to the tail gas treatment unit for treatment after dustremoval; and the ammonium chloride powder collected by calcination bedcyclone separator 6-5 is transmitted to the ammonium chloride hopper;

the gas discharged from tail gas washing absorber 7 after absorptiontreatment with an alkali solution is transmitted to chimney 9 then tovent through induced draft fan 8.

In this example, the industrial grade vanadium pentoxide powder was usedas the raw material and its chemical composition is shown in Table 1.The throughput is 70 kg/h, and the high-purity vanadium pentoxideproduct was prepared by low temperature chlorination, rectification ofvanadium oxytrichloride, gas phase ammonification and calcination.

TABLE 1 Chemical composition of the industrial grade vanadium pentoxideraw material used in the example (wt %) V₂O₅ Si Ca Al Ti Fe Mn Na K S98.8 0.0150 0.0275 0.0099 0.0260 0.0971 0.0293 0.1385 0.0714 0.1274

The operation conditions are as follows: in chlorination fluidized bedbody 2-2, the amount of the carbon powder added in the low temperaturechlorination process is 10% of the mass of the industrial grade vanadiumpentoxide powder, and in the chlorination, the operation temperature is500° C. and the average residence time of the powder is 30 min; inrectifying column 3-2, the number of trays in the rectification sectionis 5, and the number of trays in the stripping section is 10 in therectification operation, and the reflux ratio of the rectificationoperation is 40; in gas phase ammonification fluidized bed body 4-4, theoperation temperature is 130° C., the molar ratio of water vapor toammonia gas is 0.5, and the molar ratio of ammonia gas to vanadiumoxytrichloride is 4.5 in the gas phase ammonification; in calcinationfluidized bed body 6-4, the operation temperature is 400° C. and theaverage residence time of the powder is 180 min in the calcination.Under such operation conditions, the direct recovery rate of vanadiumreached 80%, and the purity of the high-purity vanadium pentoxideproduct reached 99.995 wt % (4N5).

The operation conditions are as follows: in chlorination fluidized bedbody 2-2, the amount of the carbon powder added in the low temperaturechlorination process is 20% of the mass of the industrial grade vanadiumpentoxide powder, and in the chlorination, the operation temperature is300° C. and the average residence time of the powder is 80 min; inrectifying column 3-2, the number of trays in the rectification sectionis 10, and the number of trays in the stripping section is 20 in therectification operation, and the reflux ratio of the rectificationoperation is 15; in gas phase ammonification fluidized bed body 4-4, theoperation temperature is 250° C., the molar ratio of water vapor toammonia gas is 0.8, and the molar ratio of ammonia gas to vanadiumoxytrichloride is 3.5 in the gas phase ammonification; in calcinationfluidized bed body 6-4, the operation temperature is 650° C. and theaverage residence time of the powder is 60 min in the calcination. Undersuch operation conditions, the direct recovery rate of vanadium reached81%, and the purity of the high-purity vanadium pentoxide productreached 99.999 wt % (5N).

The details which are not illustrated in detail in the present inventionbelong to the well-known technologies in the art.

Of course, the present invention can also provide a variety of examples.According to the disclosure of the present invention, those skilled inthe art can make various corresponding changes and transformationswithout departing from the spirit and essence of the present invention;however, these corresponding changes and transformations shall all fallwithin the protection scope of the claims of the present invention.

What is claimed is:
 1. A system for purifying and preparing high-purityvanadium pentoxide powder, comprising a feeding device, a lowtemperature chlorination fluidized bed, a rectification and purificationdevice, a gas phase ammonification fluidized bed, an ammoniummetavanadate feeding device, a calcination fluidized bed, a tail gaswashing absorber, an induced draft fan and a chimney; wherein thefeeding device comprises an industrial grade vanadium pentoxide hopper,an industrial grade vanadium pentoxide screw feeder, a carbon powderhopper and a carbon powder screw feeder; the low temperaturechlorination fluidized bed comprises a chlorination bed feeder, achlorination fluidized bed body, a chlorination bed cyclone separator, aflue gas heat exchanger, a flue gas condenser, a chlorination bedacid-seal tank and a chlorination bed spiral slag-discharging device;the rectification and purification device comprises a distilling still,a rectifying column, a distillate condenser, a reflux liquid collectingtank, a silicon-containing vanadium oxytrichloride storage tank, arectification section acid-seal tank, a high-purity vanadiumoxytrichloride condenser, and a high-purity vanadium oxytrichloridestorage tank; the gas phase ammonification fluidized bed comprises anammonification bed air purifier, an ammonification bed gas heater, avanadium oxytrichloride nozzle, a gas phase ammonification fluidized bedbody, an ammonification bed cyclone separator, and an ammonification beddischarger; the ammonium metavanadate feeding device comprises anammonium metavanadate hopper and an ammonium metavanadate screw feeder;the calcination fluidized bed comprises a calcination bed air purifier,a calcination bed gas heater, a calcination bed feeder, a calcinationfluidized bed body, a calcination bed cyclone separator and ahigh-purity vanadium pentoxide hopper; wherein a feed outlet at thebottom of the industrial grade vanadium pentoxide hopper is connectedwith a feed inlet of the industrial grade vanadium pentoxide screwfeeder; a feed outlet at the bottom of the carbon powder hopper isconnected with a feed inlet of the carbon powder screw feeder; and afeed outlet of the industrial grade vanadium pentoxide screw feeder anda feed outlet of the carbon powder screw feeder are both connected witha feed inlet of the chlorination bed feeder through a pipeline; a feeddischarge opening of the chlorination bed feeder is connected with afeed inlet at the upper part of the chlorination fluidized bed bodythrough a pipeline; a gas inlet at the bottom of the chlorination bedfeeder is connected with a nitrogen gas source main pipe through apipeline; the chlorination bed cyclone separator is provided at thecenter of the top of the expansion section of the chlorination fluidizedbed body; a gas outlet at the top of the chlorination bed cycloneseparator is connected with a hot flue gas inlet of the flue gas heatexchanger through a pipeline; a cold flue gas outlet of the flue gasheat exchanger is connected with a gas inlet of the flue gas condenserthrough a pipeline; a gas outlet of the flue gas condenser is connectedwith a gas inlet of the chlorination bed acid-seal tank through apipeline; a gas outlet of the chlorination bed acid-seal tank isconnected with a gas inlet of the tail gas washing absorber through apipeline; a slag-discharge opening at the lower part of the chlorinationfluidized bed body is connected with a feed inlet of the chlorinationbed spiral slag-discharging device through a pipeline; a gas inlet atthe bottom of the chlorination fluidized bed body is connected with ahot gas outlet of the flue gas heat exchanger through a pipeline; and acold gas inlet of the flue gas heat exchanger is connected with achlorine gas source main pipe, the nitrogen gas source main pipe and acompressed air main pipe through pipelines, respectively; a liquidoutlet at the bottom of the flue gas condenser is connected with a feedinlet of the rectifying column through a pipeline; a steam outlet of thedistilling still is connected with a steam inlet of the rectifyingcolumn through a pipeline; a backflow inlet of the distilling still isconnected with a liquid reflux outlet at the bottom of the rectifyingcolumn through a pipeline; a gas outlet at the top of the rectifyingcolumn is connected with a gas inlet of the distillate condenser througha pipeline; a liquid outlet of the distillate condenser is connectedwith a liquid inlet of the reflux liquid collecting tank through apipeline; a reflux liquid outlet of the reflux liquid collecting tank isconnected with a reflux liquid inlet at the top of the rectifying columnthrough a pipeline; a feed discharge opening of the reflux liquidcollecting tank is connected with an inlet of the silicon-containingvanadium oxytrichloride storage tank through a pipeline; an exhaust gasoutlet of the silicon-containing vanadium oxytrichloride storage tank isconnected with a gas inlet of the rectification section acid-seal tankthrough a pipeline; a gas outlet of the rectification section acid-sealtank is connected with a gas inlet of the tail gas washing absorberthrough a pipeline; a rectificate outlet of the rectifying column isconnected with a gas inlet of the high-purity vanadium oxytrichloridecondenser through a pipeline; a liquid outlet of the high-purityvanadium oxytrichloride condenser is connected with a liquid inlet ofthe high-purity vanadium oxytrichloride storage tank through a pipeline;and an underflow outlet is provided at the bottom of the distillingstill; a gas inlet of the ammonification bed air purifier is connectedwith the compressed air main pipe through a pipeline; a gas outlet ofthe ammonification bed air purifier is connected with a gas inlet of theammonification bed gas heater, a gas inlet of the vanadiumoxytrichloride nozzle, and a gas inlet at the bottom of theammonification bed discharger through pipelines, respectively; the gasinlet of the ammonification bed gas heater is connected with anultrapure water main pipe and a purified liquid ammonia main pipethrough pipelines; a combustion-supporting wind inlet and a fuel inletof a combustion nozzle of the ammonification bed gas heater arerespectively connected with the compressed air main pipe and a fuel mainpipe through pipelines; a gas outlet of the ammonification bed gasheater is connected with a gas inlet at the bottom of the gas phaseammonification fluidized bed body through a pipeline; a liquid outlet ofthe high-purity vanadium oxytrichloride storage tank is connected with avanadium oxytrichloride inlet of the vanadium oxytrichloride nozzlethrough a pipeline; the ammonification bed cyclone separator is providedat the center of the top of the expansion section of the gas phaseammonification fluidized bed body; a gas outlet at the top of theammonification bed cyclone separator is connected with a tail gastreatment unit through a pipeline; a feed discharge opening at the upperpart of the gas phase ammonification fluidized bed body is connectedwith a feed inlet of the ammonification bed discharger through apipeline; and a feed discharge opening of the ammonification beddischarger is connected with a feed inlet of the ammonium metavanadatehopper through a pipeline; a feed outlet at the bottom of the ammoniummetavanadate hopper is connected with a feed inlet of the ammoniummetavanadate screw feeder; and a feed discharge opening of the ammoniummetavanadate screw feeder is connected with a feed inlet of thecalcination bed feeder through a pipeline; a gas inlet of thecalcination bed air purifier is connected with the compressed air mainpipe through a pipeline; a gas outlet of the calcination bed airpurifier is connected with a gas inlet of the calcination bed gas heaterand a gas inlet at the bottom of the calcination bed feeder throughpipelines, respectively; a combustion-supporting wind inlet and a fuelinlet of a combustion nozzle of the calcination bed gas heater arerespectively connected with the compressed air main pipe and the fuelmain pipe through pipelines; a gas outlet of the calcination bed gasheater is connected with a gas inlet at the bottom of the calcinationfluidized bed body through a pipeline; a feed discharge opening of thecalcination bed feeder is connected with a feed inlet at the lower partof the calcination fluidized bed body through a pipeline; a gas outletat the top of the calcination fluidized bed body is connected with a gasinlet of the calcination bed cyclone separator through a pipeline; apowder outlet at the bottom of the calcination bed cyclone separator isconnected with a feed inlet of an ammonium chloride hopper through apipeline; a gas outlet at the top of the calcination bed cycloneseparator is connected with the tail gas treatment unit through apipeline; and a feed discharge opening at the upper part of thecalcination fluidized bed body is connected with a feed inlet of thehigh-purity vanadium pentoxide hopper through a pipeline; a gas outletof the tail gas washing absorber is connected with a gas inlet of theinduced draft fan through a pipeline; and a gas outlet of the induceddraft fan is connected with a gas inlet at the bottom of the chimneythrough a pipeline.
 2. A method for purifying and preparing high-purityvanadium pentoxide powder based on the system of claim 1, comprising thefollowing steps: allowing industrial grade vanadium pentoxide powder inthe industrial grade vanadium pentoxide hopper and carbon powder in thecarbon powder hopper to enter the chlorination bed feeder simultaneouslythrough the industrial grade vanadium pentoxide screw feeder and thecarbon powder screw feeder respectively and be mixed therein, and thenenter the chlorination fluidized bed body; allowing chlorine gas fromthe chlorine gas source main pipe, nitrogen gas from the nitrogen gassource main pipe and air from the compressed air main pipe to bepreheated by exchanging heat with chlorination flue gas by the flue gasheat exchanger, and then enter the chlorination fluidized bed body toallow the vanadium pentoxide and the carbon powder to be kept at afluidized state and chemically reacted, wherein the air enables a partof the carbon powder to combust to provide heat for maintaining thetemperature of the fluid bed, and the chlorine gas and the carbon powderfunction together to make vanadium pentoxide and a small amount ofimpurities chlorinated, to form chlorinated residues and chlorinationflue gas rich in vanadium oxytrichloride; discharging the chlorinatedresidues through the slag-discharge opening at the lower part of thechlorination fluidized bed body and the chlorination bed spiralslag-discharging device in turn; and allowing the chlorination flue gasto be subjected to dust removing by the chlorination bed cycloneseparator and fall back to the chlorination fluidized bed body, and thenbe precooled by the flue gas heat exchanger and enter the flue gascondenser, such that vanadium oxytrichloride therein is condensed toform a crude vanadium oxytrichloride liquid and the remaining tail gasenters the tail gas washing absorber through the chlorination bedacid-seal tank; allowing the crude vanadium oxytrichloride liquid formedby the flue gas condenser to enter the rectifying column and thedistilling still to be subjected to rectification operation, to obtain avanadium-rich waste rich in high-boiling-point impurities,silicon-containing vanadium oxytrichloride vapor rich inlow-boiling-point impurities and high-purity vanadium oxytrichloridevapor; condensing the silicon-containing vanadium oxytrichloride vaporinto liquid by the distillate condenser, wherein a part of the liquidreturns to the rectifying column-through the reflux liquid collectingtank, and the remaining liquid enters the silicon-containing vanadiumoxytrichloride storage tank; transmitting the exhaust gas produced inthe silicon-containing vanadium oxytrichloride storage tank to the tailgas washing absorber through the rectification section acid-seal tank;and condensing the high-purity vanadium oxytrichloride vapor into liquidby the high-purity vanadium oxytrichloride condenser and allowing theliquid to enter the high-purity vanadium oxytrichloride storage tank;allowing the high-purity vanadium oxytrichloride from the high-purityvanadium oxytrichloride storage tank to be carried by purified air fromthe ammonification bed air purifier into the gas phase ammonificationfluidized bed body via the vanadium oxytrichloride nozzle; preheatingultrapure water, purified liquid ammonia and the purified air by theammonification bed gas heater and then transmitting them to the gasphase ammonification fluidized bed body, to keep the powder in the bedat a fluidized state and subject vanadium oxytrichloride to hydrolysisand ammonification to generate ammonium metavanadate powder containingammonium chloride, wherein the ammonium metavanadate powder containingammonium chloride enters the ammonium metavanadate hopper afterdischarged by the ammonification bed discharger, and the producedammonia-containing ammonified flue gas is subjected to dust removing bythe ammonification bed cyclone separator and then transmitted to thetail gas treatment unit for treatment; allowing the ammoniummetavanadate powder containing ammonium chloride in the ammoniummetavanadate hopper to enter the calcination fluidized bed body throughthe ammonium metavanadate screw feeder and the calcination bed feeder inturn; allowing compressed air to be purified by the calcination bed airpurifier and preheated by the calcination bed gas heater in turn andthen enter the calcination fluidized bed body, to keep the powder in thebed at a fluidized state and subject the ammonium metavanadate materialcontaining ammonium chloride to thermal decomposition to obtain ahigh-purity vanadium pentoxide powder product, and allowing the productto enter the high-purity vanadium pentoxide hopper through the feeddischarge opening at the upper part of the calcination fluidized bedbody; allowing the calcination flue gas produced by the calcinationdecomposition to enter the calcination bed cyclone separator and becooled down to separate out ammonium chloride, and transmitting thecalcination flue gas to the tail gas treatment unit for treatment afterdust removal; and transmitting the ammonium chloride powder collected bythe calcination bed cyclone separator to the ammonium chloride hopper;transmitting the gas discharged from the tail gas washing absorber afterabsorption treatment with an alkali solution to the chimney then to ventthrough the induced draft fan.
 3. The method for purifying and preparinghigh-purity vanadium pentoxide powder according to claim 2, wherein inthe chlorination fluidized bed body, the amount of the carbon powderadded in the chlorination process is 10%-20% of the mass of theindustrial grade vanadium pentoxide powder.
 4. The method for purifyingand preparing high-purity vanadium pentoxide powder according to claim2, wherein in the chlorination fluidized bed body, the operationtemperature is 300-500° C. and the average residence time of the powderis 30-80 min in the chlorination.
 5. The method for purifying andpreparing high-purity vanadium pentoxide powder according to claim 2,wherein in the rectifying column, the number of trays in therectification section is 5-10, and the number of trays in the strippingsection is 10-20 in the rectification operation.
 6. The method forpurifying and preparing high-purity vanadium pentoxide powder accordingto claim 2, wherein the reflux ratio of the rectification operation is15-40.
 7. The method for purifying and preparing high-purity vanadiumpentoxide powder according to claim 2, wherein in the gas phaseammonification fluidized bed body, ammonium metavanadate is prepared bygas phase ammonification of the high-purity vanadium oxytrichloride, andin the gas phase ammonification, the operation temperature is 130-250°C., the molar ratio of water vapor to ammonia gas is 0.5-0.8, and themolar ratio of ammonia gas to vanadium oxytrichloride is 3.5-4.5.
 8. Themethod for purifying and preparing high-purity vanadium pentoxide powderaccording to claim 2, wherein in the calcination fluidized bed body, thethermal decomposition of the ammonium metavanadate containing ammoniumchloride is achieved by fluidization calcination, and in thecalcination, the operation temperature is 400-650° C., and the averageresidence time of the powder is 60-180 min.